Analyses of functions of proteins existing in the body are important tasks. Methods for identifying and quantifying these expressed proteins satisfy the wide social demands from the clarification of cell functions in the research field to the diagnoses and therapies in the medical field. As means for identifying and quantifying proteins, methods utilizing antibodies and various biosensor systems utilizing arrays of specific proteins are known.
The concept for developing the conventional protein chips is based on immobilization of proteins or fragments thereof, whose structures are known. Immobilization of antibody molecules is also based on this concept. By this method, quantification of the loading amount is problematic, and uniform immobilization is difficult. Particularly, since the yield of immobilization (loading amount) is generally low and depends on the properties of the peptide fragments, the method lacks reliability and so wide use thereof is prevented. Further, in cases where protein fragments are used, the sites of cleavage are restricted because of specificities of the cleavage (if the proteins are cleaved without specificities, the resultants are random fragments and so the molecules immobilized on the chips cannot be identified), thus, free design can not be accomplished. Still further, the thus immobilized proteins have structures different from those in the body, and may not have the structures indispensable for attaining the desired recognitions. These are problems in practice.
Methods for analyzing interactions between peptides and proteins in solutions using fluorometer or the like are known. However, with these methods, considerable amount of samples are necessary, so that a long time is required for sample preparation. Recently, methods such as surface plasmon or the like are used. However, the apparatuses are expensive, the sensitivities are generally low, and simple measurements at local places cannot be attained. Thus, by the conventional methods, treatments of numerous samples are difficult.